1. Field of the Invention
The present invention relates to a receiver, signal receiving method, and information recording medium which records a program for receiving data signals. More particularly, the present invention relates to a receiver and method for desirably estimating transmission path characteristics when to transmit a signal including a data signal and a known signal, compensating for the signal, and suitably obtaining the transmitted data signal, and also to a computer readable recording medium which records a program for realizing the receiver and method in a computer.
2. Description of the Related Art
In recent years, in the field of radio communications, it is more demanded that a large amount of data are transmitted. In response to this demand, various techniques have been studied.
Since delayed waves may occur as a result of reflection caused by an electro-magnetic wave obstacle in a transmission path, it is necessary to eliminate any undesired effects of the occurring delayed waves. In consideration of this, the following technique is proposed.
On the transmitter side, data symbols to be transmitted are modulated together with a known symbol, so as to be transmitted.
On the receiver side, a portion of a received signal which corresponds to the known symbol is compared with a resultant signal obtained by modulating the known symbol, so as to obtain an impulse response. Thus obtained impulse response is estimated as transmission path characteristics. Further, a portion of the received signal which corresponds to the data symbol is compensated using the estimated transmission path characteristics, and demodulated, so as to obtain the transmitted data symbol.
Such a technique is used in the OFDM (Orthogonal Frequency Division Multiplexing) communications.
To transmit a large amount of data through a mobile radio LAN (Local Area Network), it is desirable that the length of the transmitted data symbol is larger than the length of the known symbol as much as possible. In the field of mobile data communications, transmission contexts between a terminal and another terminal and between a terminal and a base station may widely change.
According to the above-described technique, the transmission path characteristics change as time goes by. In such circumstances, the estimated value of the transmission path characteristics may be quite far from the actual contexts while transmitting a data symbol which is large in length. A problem arises in that the data can not sufficiently be compensated.